diff options
Diffstat (limited to 'share/man')
| -rw-r--r-- | share/man/man4/udcf.4 | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/share/man/man4/udcf.4 b/share/man/man4/udcf.4 index 9529d3467da..78fa6f8af92 100644 --- a/share/man/man4/udcf.4 +++ b/share/man/man4/udcf.4 @@ -1,4 +1,4 @@ -.\" $OpenBSD: udcf.4,v 1.16 2006/12/09 13:13:55 jmc Exp $ +.\" $OpenBSD: udcf.4,v 1.17 2006/12/09 13:27:05 mbalmer Exp $ .\" .\" Copyright (c) 2006 Marc Balmer <mbalmer@openbsd.org> .\" @@ -89,13 +89,13 @@ The driver was written by .An Marc Balmer Aq mbalmer@openbsd.org . .Sh CAVEATS -DCF uses a 77KHz long wave radio signal transmitted from near Frankfurt, +DCF uses a 77.5 kHz long wave radio signal transmitted from near Frankfurt, Germany. -Up to about 900km, the radio signal can travel directly to the receiver, +Up to about 900 km, the radio signal can travel directly to the receiver, providing a linearly increasing time offset based on distance. Due to the curvature of the Earth, beyond this distance the signal must -bounce off the lower ionosphere (residing at approximately 70km elevation -during the day, and 90km at night), thus causing a non-linearly increasing +bounce off the lower ionosphere (residing at approximately 70 km elevation +during the day, and 90 km at night), thus causing a non-linearly increasing time offset which can only be roughly calculated using trigonometry. Since the distance and transmission geometry is not known, the clock receivers and @@ -103,6 +103,6 @@ the clock receivers and driver currently make no effort to calculate this offset. We simply assume that the offset is small. .Pp -In Germany, the train system uses DCF clocks. +In Germany, the train system uses DCF77 clocks. As the distance from Frankfurt increases, trains can be expected to run later. |